Vibration and dynamic acceleration sensing using capacitors

ABSTRACT

The present disclosure relates to an apparatus comprising at least one sensing capacitor and a controller, wherein the controller is configured to receive a signal from the at least one sensing capacitor indicative of a change of charge of the sensing capacitor, and wherein the controller is configured to determine an amount of force applied to the sensing capacitor, an acceleration of the sensing capacitor, a torsion of the sensing capacitor, a vibration of the sensing capacitor or a pulling force applied to the sensing capacitor based on the change of charge of the at least one sensing capacitor.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/136,145 filed Dec. 20, 2013, which claims the benefit of U.S.Provisional Patent Application No. 61/869,952, filed Aug. 26, 2013, allof which are incorporated herein by reference in their entirety.

FIELD

This disclosure relates to the measuring of a force, a vibration or atorsion applied to a force sensor. More specifically, the examples ofthe present disclosure relate to measuring the charge of a sensingcapacitor and determining a force, a vibration or a torsion applied tothe sensing capacitor based on said change of charge.

BACKGROUND

An apparatus that is configured to sense a mechanical force requires asensing element. It is known in the state of the art to use piezosensors or micro-optoelectro-mechanical systems sensors (MEMS sensors)for measuring mechanical forces. In addition, it is known in the stateof the art to use capacitors to sense mechanical forces. To measure amechanical force with the help of the known sensing capacitors thecapacitance change is detected and the mechanical forces are determinedbased on the change of capacitance of the sensing capacitors. Accordingto one example, at least one of the conductors of a capacitor like aplate of a plate-type capacitor is moveable relative to the dielectricin response to an applied mechanical force. Thereby, the capacitance ofthe capacitor changes and based on said change of capacitance theapplied mechanical force can be determined.

One disadvantage of the known sensing elements for mechanical forces isthat they have to be individualized to each type of application.Furthermore, the sensing capacitors known that allow a measurement ofmechanical forces based on their change of capacitance are expensivecompared to standard capacitors.

Moreover, said piezo and MEMS sensors may not be mounted to printedcircuit board using integrated process technology easily. For example,piezo sensors are sensitive to heat and soldering cables may damage thepiezo sensors. Furthermore, MEMS sensors may not be capable to respondto high frequencies.

It is therefore one objective of the present disclosure to overcome theproblems of measuring mechanical forces by a sensor that may be coupledto a circuit board by using integrated process technology easily andthat is of low costs. Another object of the present invention is toprovide a sensor that allows a measuring of mechanical forces with ahigh frequency response.

SUMMARY

One aspect of the present disclosure is an apparatus comprising at leastone sensing capacitor and a controller. The controller may be configuredto receive a signal from the at least one sensing capacitor indicativeof a change of charge of the sensing capacitor. The controller may beconfigured to determine an amount of force applied to the sensingcapacitor, an acceleration of the sensing capacitor, a torsion of thesensing capacitor, a vibration of the sensing capacitor and/or a pullingforce applied to the sensing capacitor based on the change of charge ofthe at least one sensing capacitor.

The use of a signal from the sensing capacitor indicative of a change ofcharge of the sensing capacitor for determining mechanical forces allowsto provide a low power consumption apparatus. Moreover, the used sensingcapacitor is very cheap compared to piezo sensors or MEMS sensors, andmay be coupled to a circuit board by using integrated process technologyeasily.

The change of charge of the sensing capacitor is based on the piezoeffect. In general, said piezo effect of capacitors is recognized due toa decrease of capacitance depending on the DC voltage of a capacitor.

Therefore, standard capacitors like ceramic or silicon capacitorswithout moveable elements may be used as sensing capacitors according tothe present disclosure for measurement of mechanical forces.

The piezo effect of a capacitor depends on its dielectric. For example,capacitors having Y5V or X7R as their dielectric are highly sensitive toapplied mechanical forces, whereas e.g. capacitors having NP0 as thedielectric are less sensitive to applied mechanical forces.

According to one example of the present disclosure, a capacitor may haveY5V or X7R as the dielectric.

According to one example of the present disclosure, a charge amplifiermay be connected between the at least one sensing capacitor and thecontroller.

Thereby, it may be of advantage to provide a charge amplifier optimizedfor low noise and high density.

According to one example of the present disclosure, the charge amplifiercomprises at least a first operational amplifier. According to thisexample, at least one first capacitor may be connected between theoutput of the operational amplifier and the inverting input of the firstoperational amplifier.

In the alternative, according to one example of the present disclosurethe charge amplifier may comprise at least a first and at least a secondoperational amplifier, wherein the inverting input of the firstoperational amplifier may be connected to the first terminal of the atleast one sensing capacitor and the inverting input of the secondoperational amplifier may be connected to the second terminal of the atleast one sensing capacitor. The first capacitor may be connectedbetween the output of the first operational amplifier and the invertinginput of the first operational amplifier and the second capacitor may beconnected between the output of the second operational amplifier and theinverting input of the second operational amplifier.

According to one example, a third operational amplifier may be connectedto the output of the first and the second operational amplifier.Thereby, the third operational amplifier may provide a furtheramplification of the signal from the at least one sensing capacitorindicative of a change of charge of the sensing capacitor and areduction of noise.

The input impedance of a charge amplifier according to the presentexamples may be very high. It may pickup the 50 Hz or 60 Hz signals fromthe mains if the sensing capacitor and the charge amplifier may becoupled within an electric circuit. This pickup may be higher in case oflong connecting lines between the sensing capacitor and the chargeamplifier. According to one example of the present disclosure, theconnecting lines between the sensing capacitor and the charge amplifiermay reside between ground connecting lines to provide a good shieldingand reducing the pickup.

According to one example of the present disclosure, the at least onesensing capacitor may be coupled to a printed circuit board (PCB).

This may provide an easy and cheap possibility to couple the sensingcapacitor with the charge amplifier and other electric devices. A PCBmay mechanically support and electrically connect electronic componentsusing conductive tracks, pads and other. A PCB may be provided usingmaterials like laminates, copper-clad laminates, resin impregnatedB-stage cloth (Pre-preg), copper foil or ceramic.

According to another example of the present disclosure, the PCB maycomprise cuts in form of segments of a circle, wherein at least a firstand at least a second cut may be arranged symmetrically and mirroredaround the centre of the circle, and wherein the at least one sensingcapacitor may be coupled to the PCB at the centre of the circle orbetween the first and the second cuts.

This example allows a movement of the centre of the circle and thesensing capacitor coupled thereto as a sensing area relative to theremaining parts of PCB. The measurable voltage amplitude of the sensingcapacitor is linear to dynamic forces applied to the sensing area.Therefore, an acceleration measurement or a force sensitive button maybe provided according to this example.

According to one example of the present invention an inertia may becoupled to the PCB at the centre of the circle. For example, a chargeamplifier or parts of a charge amplifier are connected between the atleast one sensing capacitor and the controller and the charge amplifieror parts of the charge amplifier coupled to the PCB at the centre of thecircle.

Such an inertia may be of advantage to improve the movement of thesensing area in reaction to applied mechanical forces and therefore mayallow improved measurement results.

According to the example, the controller may be configured to determinean amount of force applied to the sensing capacitor or an accelerationof the sensing capacitor applied to the sensing capacitor based on thechange of charge of the at least one sensing capacitor.

According to another example of the present disclosure, the PCB maycomprise at least two longitudinal cuts arranged in parallel to eachother, and wherein the at least one sensing capacitor is coupled to thePCB between and equally spaced from the at least two longitudinal cuts.

It is obvious for those skilled in the art that multiple sensingcapacitors may be arranged on the PCB. For example, a first sensingcapacitor may be arranged between first cuts arranged in parallel toeach other and a second sensing capacitor may be arranged between secondcuts arranged in parallel to each other, and wherein the first and thesecond cuts are arranged shifted, rotated, parallel or vertical to eachother.

According to this example, a charge amplifier or parts of a chargeamplifier are connected between the at least one sensing capacitor andthe controller is coupled to the PCB between and in equally spaced fromthe at least two longitudinal cuts.

Furthermore, according to this example, the controller may be configuredto determine an amount of force applied to the sensing capacitor or anacceleration of the sensing capacitor applied to the sensing capacitorbased on the change of charge of the at least one sensing capacitor.

According to another example of the present disclosure, a first sensingcapacitor may be coupled to a first side of the PCB and a second sensingcapacitor may be coupled to a second side opposite to the first side ofthe PCB, wherein the first and the second sensing capacitor are coupledto the PCB adjacent or directly opposite to each other.

This arrangement of at least two sensing capacitors may allow adifferential measurement.

Thereby, the PCB may be of a longitudinal shape having a first end and asecond end opposite to the first end and two longitudinal ends, whereinthe first end may be affixable and the second end may be moveable, andwherein a charge amplifier or parts of a charge amplifier may beconnected between the at least one sensing capacitor and the controller,and wherein the controller may be coupled to the PCB adjacent to thefirst end. The first and the second sensing capacitors may be coupled ina first distance from the first end to the PCB.

According to this example, the controller may be configured to determinean oscillation of the PCB based on an amount of force applied to thefirst and the second sensing capacitor based on the change of charge ofthe first and the second sensing capacitor.

According to another example of the present disclosure, the PCB may beof a longitudinal shape having a first end and a second end opposite tothe first end and two longitudinal ends, wherein the first end isaffixable and the second end may be rotatable, and wherein the twoconductors and the dielectric of the at least one sensing capacitor maybe coupled to the PCB vertically to the rotation axis of the PCB.

By arranging the two conductors and the dielectric of sensing capacitorin parallel to the torsion forces applied to the PCB said torsion forcesmay be measured.

According to this example, the controller may be configured to determinea torsion force applied to the sensing capacitor based on the change ofcharge of the at least one sensing capacitor.

According to another example, the PCB may be of a longitudinal shapehaving a first end and a second end opposite to the first end and twolongitudinal ends, wherein the first end is affixable and the second endmay be rotatable, and wherein the at least one sensing capacitor may becoupled to the PCB adjacent to and spaced from the first end of the PCBin a first distance, and wherein the charge amplifier may be coupled tothe PCB adjacent to and spaced from the first end of the PCB in a seconddistance, the second distance being smaller than the first distance.

According to this example the controller may be configured to determinea vibration of the sensing capacitor based on the change of charge ofthe at least one sensing capacitor.

According to another example of the present disclosure, the PCB may bearranged within a pressure cell, and wherein the PCB may divide thepressure cell into a first and a second pressure chamber, and whereinthe first pressure chamber may comprise a first opening for applying afirst pressure to the first pressure chamber and the second pressurechamber may comprise a second opening for applying a second pressure tothe second pressure chamber, and wherein a first sensing capacitor maybe coupled to a first side of the PCB and a second sensing capacitor maybe coupled to a second side opposite to the first side of the PCB,wherein the first and the second sensing capacitor may be coupled to thePCB adjacent or directly opposite to each other.

According to this example, the controller may be configured to determinea differential pressure applied to the first and the second sensingcapacitor based on the change of charge of the first and the secondsensing capacitor.

According to another example of the present disclosure, the PCB may beof a longitudinal shape having a first end and a second end opposite tothe first end and two longitudinal ends, wherein the first end may beaffixable and the second end may be moveable, and wherein the twoconductors and the dielectric of the at least one sensing capacitor maybe coupled to the PCB in parallel to the two longitudinal ends.

According to this example, the controller may be configured to determinea pulling force applied to the second end of the PCB based on the changeof charge of the at least one sensing capacitor.

According to one example of the present disclosure, the at least onesensing capacitor is a ceramic capacitor or a silicon capacitor.

Ceramic capacitors and silicon capacitors provide a pizeo effect that ismeasurable by a change of charge of the respective capacitor, whereinstandard capacitors may be used.

According to another example of the present disclosure the at least onesensing capacitor is coupled to the PCB by using integrated circuittechnology.

This may reduce the cost during manufacturing.

According to another example of the present disclosure a methodcomprising the steps measuring a change of charge of a of a sensingcapacitor; and determining an amount of force applied to the sensingcapacitor, an acceleration of the sensing capacitor, a torsion of thesensing capacitor, a vibration of the sensing capacitor or a pullingforce applied to the sensing capacitor based on the change of charge ofthe at least one sensing capacitor is provided.

According to one example of the present disclosure, the method mayemploy an apparatus according to one example of the present disclosure.

According to one example, an apparatus according to the presentdisclosure may be used for flow sensing, both Vortex or turbulencesensing, bearing wear monitoring and/or acceleration sensing, sensing ofstrain gauges and/or vibration sensing. In addition to, the apparatusmay be used as a knock sensor, e.g. to make mobile devices detectknocks, e.g. a watch that triggers functions when knocked on by afinger. Thereby, for example, according to one example a knocking on aplate may be localized by the help of a triangulation. A possible use ofsuch a triangulation may for example be a user interface behind amassive plate. Such a user interface is not realizable with thecapacitive sensors known in the state of the art. Another example of ause of an apparatus according to the present disclosure may be themeasurement of rotation speed by harmonic analysis and/or to detect thedirection of an impact and/or an acceleration with multiple sensors.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates an example apparatus of vibration and dynamicacceleration sensing using capacitors;

FIG. 2 illustrates another example apparatus of vibration and dynamicacceleration sensing using capacitors;

FIG. 3 illustrates a further example apparatus of vibration and dynamicacceleration sensing using capacitors;

FIG. 4 illustrates a yet further example of an apparatus of vibrationand dynamic acceleration sensing using capacitors;

FIG. 5 illustrates a still yet further example of an apparatus ofvibration and dynamic acceleration sensing using capacitors;

FIG. 6 illustrates a yet further example of an apparatus of vibrationand dynamic acceleration sensing using capacitors including a firstsensing capacitor, a second sensing capacitor and a charge amplifiercoupled to a PCB;

FIG. 7 illustrates a an apparatus of vibration and dynamic accelerationsensing using capacitors including a first sensing capacitor and acharge amplifier coupled to a PCB.

FIG. 8 illustrates a first charge amplifier;

FIG. 9 illustrates a second charge amplifier;

FIG. 10a illustrates an example apparatus according to the presentdisclosure;

FIG. 10b illustrates a resultant testing of FIG. 10a with respect toapplied mechanical forces;

FIG. 11a illustrates an apparatus of an example of vibration and dynamicacceleration testing;

FIG. 11b illustrates a first resulting waveform of a test of theapparatus of FIG. 11a ; and

FIG. 11c illustrates a second resulting waveform of a test of theapparatus of FIG. 11 a.

DETAILED DESCRIPTION OF THE DRAWINGS

While illustrative examples are illustrated and described below, it willbe appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the disclosure. In that regard,the detailed description set forth below, in connection with theappended drawings is intended only as a description of various examplesof the disclosed subject matter and is not intended to represent theonly examples. Each example described in this disclosure is providedmerely as an example or illustration and should not be construed aspreferred or advantageous over other examples. The illustrative examplesprovided herein are not intended to be exhaustive or to limit thedisclosure to the precise forms disclosed. Similarly, any stepsdescribed herein may be interchangeable with other steps, orcombinations of steps, in order to achieve the same or substantiallysimilar result.

Examples of the present disclosure may be practiced with an apparatusshown in FIG. 1. The apparatus 1 comprises one sensing capacitor 3 and acontroller 5. The controller 5 is configured to receive a signal fromthe sensing capacitor 3 indicative of a change of charge of the sensingcapacitor 3. Based on said signal, the controller 5 is configured todetermine an amount of force applied to the sensing capacitor 3, inparticular an acceleration of the sensing capacitor 3. The sensingcapacitor 3 is thereby coupled to a printed circuit board (PCB) 9.

A charge amplifier 7 is connected between the sensing capacitor 3 andthe controller 5 to amplify the signal sensed by the controller 5. ThePCB 9 comprise cuts 11 in form of segments of a circle, wherein firstcuts 11 and second cuts 11′ are arranged symmetrically and mirroredaround the centre of the circle.

The apparatus according to FIG. 1 may therefore allow a movement of thecentre of the circle and the sensing capacitor 3 coupled between thefirst and the second cuts 11, 11′ as a sensing area relative to theremaining parts of PCB 9. The charge amplifier 7 is thereby coupled tothe PCB as inertia for the sensing capacitor 3

The measurable voltage amplitude of the sensing capacitor 3 is linear todynamic forces applied to the sensing area. Therefore, for example anacceleration measurement or a force sensitive button may be provided.

Examples of the present disclosure may further be practiced with anapparatus shown in FIG. 2.

The apparatus 10 according to FIG. 2 comprises a sensing capacitor 3 anda charge amplifier 7. The sensing capacitor 3 and the charge amplifier 7are couple to a PCB 9′. The PCB 9′ comprises two longitudinal cuts 13arranged in parallel to each other. As shown in FIG. 2, the sensingcapacitor 3 and the charge amplifier 7 are coupled to the PCB 9′ betweenand equally spaced from the two longitudinal cuts 13. The chargeamplifier 7 is further connected between the sensing capacitor 3 and thecontroller 5 to amplify a signal sensed by the controller 5representative for a change of charge of the sensing capacitor 3.

The controller 3 may be configured to determine an amount of forceapplied to the sensing capacitor 3 or an acceleration of the sensingcapacitor 3 applied to the sensing capacitor 3 based on the change ofcharge of the at least one sensing capacitor 3.

Examples of the present disclosure may further be practiced with anapparatus shown in FIG. 3.

The apparatus 20 according to FIG. 3 comprises a first and a secondsensing capacitor 3, 15 and a charge amplifier 7 coupled to a PCB 9″.

The first sensing capacitor 3 is coupled to a first side 17 of the PCB9″ and the second sensing capacitor 15 is coupled to a second side 19opposite to the first side 17 of the PCB 9″, wherein the first and thesecond sensing capacitor 3, 15 are coupled to the PCB 9″ directlyopposite to each other. This arrangement of the first and the secondsensing capacitor 3, 15 allows a differential measurement.

Thereby, the PCB 9″ is of a longitudinal shape having a first end 21 anda second end 23 opposite to the first end 21. The first end 21 is fixedand the second end 23 is moveable. According to this example, thecontroller 5 is configured to determine an oscillation of the PCB 9″based on an amount of force applied to the first and the second sensingcapacitor 3, 15 based on the change of charge of the first and thesecond sensing capacitor 3, 15. A possible employment of an apparatusaccording to FIG. 3 may be a Vortex flowmeter, wherein the oscillationof the second end 23 of the PCB 9″ may be proportional to the volumeflow rate to be measured. For amplification of the signal representativeof the change of charge of the first and the second sensing capacitor 3,15 a charge amplifier is connected between said two sensing capacitors3, 15 and the controller 5.

The apparatus 30 according to FIG. 4 comprises a sensing capacitor 3′and a charge amplifier 7 coupled to a PCB 9.

The PCB 9 is of a longitudinal shape having a first end 21 and a secondend 23 opposite to the first end and two longitudinal ends 25, 27,wherein the first end 21 is fixed and the second end 23 is rotatable.The two conductors and the dielectric of the sensing capacitor 3′ iscoupled to the PCB 9 vertically to the rotation axis A of the PCB 9. Byarranging the two conductors and the dielectric of the sensing capacitor3′ in parallel to the torsion forces applied to the PCB β, said torsionforces may be measured. The controller 5 is configured to determine atorsion force applied to the sensing capacitor 3′ based on the change ofcharge of the sensing capacitor 3′.

The apparatus 40 according to FIG. 5 comprises a sensing capacitor 3″and a charge amplifier 7 coupled to a PCB 9.

The PCB 9 may be of a longitudinal shape having a first end 21 and asecond end 23 opposite to the first end and two longitudinal ends 25,27, wherein the first end 21 is fixed and the second end 21 is moveable.The sensing capacitor 3″ is coupled to the PCB 9 adjacent to and spacedfrom the first end 21 of the PCB 9 in a first distance, and wherein thecharge amplifier 7 is coupled to the PCB 9 adjacent to and spaced fromthe first end 21 of the PCB in a second distance. The controller 5 isconfigured to determine a vibration of the sensing capacitor 3″ based onthe change of charge of the at least one sensing capacitor.

The apparatus 50 according to FIG. 6 comprises a first sensing capacitor3, a second sensing capacitor 15 and a charge amplifier 7 coupled to aPCB 9.

The PCB 9 is arranged within a pressure cell 28 and divides the pressurecell 28 into a first and a second pressure chamber 29, 33. The firstpressure chamber 29 comprises a first opening 31 for applying a firstpressure to the first pressure chamber 29 and the second pressurechamber 33 comprises a second opening 35 for applying a second pressureto the second pressure chamber 33. The first sensing capacitor 3 iscoupled to a first side of the PCB 9 and the second sensing capacitor 15is coupled to a second side opposite to the first side of the PCB 9. Thefirst and the second sensing capacitor 3, 15 are coupled to the PCB 9directly opposite to each other. According to this example, thecontroller 5 is configured to determine a differential pressure appliedto the first and the second sensing capacitor 3, 15 based on the changeof charge of the first and the second sensing capacitor 3, 15.

The apparatus 60 according to FIG. 7 comprises a first sensing capacitor3′″ and a charge amplifier 7 coupled to a PCB 9. The PCB 9 is of alongitudinal shape having a first end 21 and a second end 23 opposite tothe first end and two longitudinal ends 25, 27. The first end 21 isfixed and the second end 23 is moveable. The two conductors and thedielectric of the sensing capacitor 3′″ are coupled to the PCB 9 inparallel to the two longitudinal ends 25, 27. The controller 5 isthereby configured to determine a pulling force applied to the secondend 23 of the PCB 9 based on the change of charge of the sensingcapacitor 3′″.

The examples of the present disclosure according to FIGS. 1 to 7 mayemploy a ceramic capacitor or a silicon capacitor as the first or secondsensing capacitor. Thereby, according to one example, the first and thesecond sensing capacitor may be coupled to the PCB by using integratedcircuit technology.

FIGS. 8 and 9 show examples of charge amplifiers according to thepresent disclosure. A charge amplifier 7 according to FIG. 8 comprises afirst operational amplifier 37 and a first capacitor 39. The firstcapacitor 39 is connected between the output of the operationalamplifier 37 and the inverting input of the first operational amplifier37. The sensing capacitor 3 is connected between the inverting and thenon-inverting of the operational amplifier 37 for amplification of thesignal representative for the charge of the sensing capacitor 3.

An alternative charge amplifier 41 is shown in FIG. 9. The chargeamplifier 41 comprises a first and a second operational amplifier 43,45, wherein the inverting input of the first operational amplifier 41 isconnected to the first terminal of the at least one sensing capacitor 3and the inverting input of the second operational amplifier 45 isconnected to the second terminal of the at least one sensing capacitor3, and wherein the first capacitor 47 is connected between the output ofthe first operational amplifier 43 and the inverting input of the firstoperational amplifier 43 and the second capacitor 47 is connectedbetween the output of the second operational amplifier 45 and theinverting input of the second operational amplifier 45. A thirdoperational amplifier 51 is connected to the output of the first and thesecond operational amplifier 43, 45. Thereby, a differential amplifierin form of the first and the second operational amplifier 43, 45 and asubsequent third chopper operational amplifier 51 are provided. Such adifferential measurement of the charge of the sensing capacitor by thefirst and the second operational amplifier 43, 45 may be of advantage toreduce disturbances. In case of both the first and the secondoperational amplifier 43, 45 having the same input impedance,disturbances capacitively coupled into may automatically be subtractedand therefore eliminated. The third chopper operational amplifier 51 maybe of advantage in particular in case of the first and the secondoperational amplifier 43, 45 having a low amplification and the thirdoperational amplifier 51 has a high amplification. Thereby, flickernoise may be reduced and the signal to noise ration may be improvedsignificantly. FIG. 10a show an example of an apparatus 53 according tothe present disclosure and the waveform in FIG. 10b of testing of suchan apparatus with respect to applied mechanical forces. A sensingcapacitor 3 and a charge amplifier 5 are coupled to a PCB 9. The firstend 57 of the PCB 9 is fixed and the second end 59 of the PCB ismoveable. The length D of the PCB is 5 cm. The charge amplifier comprisea operational amplifier with a 520 pF feedback capacitor and the sensingcapacitor is a ceramic capacitor 1 UF, 50V, X7R, 0805. The second end 59of the PCB was bended up and down about 1 mm resulting in a change ofcharge of the sensing capacitor 3 as shown in FIG. 10b . Thereby it isproven that based on the change of charge of the sensing capacitor 3deflection of the moveable second end 59 of the PCB 9 can be detectedprecisely.

FIG. 11a , shows an example of an apparatus 63 according to the presentdisclosure FIGS. 11b and 11c show the first and second testing of suchan apparatus with respect to applied mechanical forces. The differencebetween the apparatus shown in FIG. 10b is that both the first and thesecond end 57, 59 are fixed. By knocking on the PCB next to the chargeamplifier 7 at 63, a positive slope 65 shown in FIG. 11b can be detectedbased on a change of charge of the sensing capacitor 3. By knocking onthe back side of the PCB 9, a negative slope 67 shown in FIG. 11c can bedetected.

As a result, with an apparatus according to the present disclosure basedon the change of charge of a sensing capacitor mechanical forces can bemeasured precisely.

1. Apparatus comprising: at least one sensing capacitor, and acontroller, wherein the controller is configured to receive a signalfrom the at least one sensing capacitor indicative of a change of chargeof the sensing capacitor, and wherein the controller is configured todetermine an amount of force applied to the sensing capacitor, anacceleration of the sensing capacitor, a torsion of the sensingcapacitor, a vibration of the sensing capacitor or a pulling forceapplied to the sensing capacitor based on the change of charge of the atleast one sensing capacitor.
 2. Apparatus according to claim 1, furthercomprising a charge amplifier connected between the at least one sensingcapacitor and the controller.
 3. Apparatus according to claim 2,characterized in that the charge amplifier comprises at least a firstoperational amplifier.
 4. Apparatus according to claim 3, furthercomprising at least one first capacitor is connected between the outputof the operational amplifier and the inverting input of the firstoperational amplifier.
 5. Apparatus according to claim 2, characterizedin that the charge amplifier comprises at least a first and at least asecond operational amplifier, wherein the inverting input of the firstoperational amplifier is connected to the first terminal of the at leastone sensing capacitor and the inverting input of the second operationalamplifier is connected to the second terminal of the at least onesensing capacitor, and wherein the first capacitor is connected betweenthe output of the first operational amplifier and the inverting input ofthe first operational amplifier and the second capacitor is connectedbetween the output of the second operational amplifier and the invertinginput of the second operational amplifier.
 6. Apparatus according toclaim 5, characterized in that a third operational amplifier isconnected to the output of the first and the second operationalamplifier.
 7. Apparatus according to claim 1, characterized in that theat least one sensing capacitor is coupled to a printed circuit board(PCB).
 8. Apparatus according to claim 7, characterized in that the PCBcomprises cuts in form of segments of a circle, wherein at least a firstand at least a second cut are arrange symmetrically and mirrored aroundthe centre of the circle, and wherein the at least one sensing capacitoris coupled to the PCB at the centre of the circle or between the firstand second cuts.
 9. Apparatus of claim 7, further comprising: an inertiais coupled to the PCB at the centre of the circle. a charge amplifier orparts of a charge amplifier are connected between the at least onesensing capacitor and the controller and the charge amplifier or partsof the charge amplifier are coupled to the PCB at the centre of thecircle. wherein the controller is configured to determine an amount offorce applied to the sensing capacitor or an acceleration of the sensingcapacitor applied to the sensing capacitor based on the change of chargeof the at least one sensing capacitor, and a charge amplifier or partsof a charge amplifier are connected between the at least one sensingcapacitor and the controller is coupled to the PCB between and inequally spaced from the at least two longitudinal cuts.
 10. Apparatusaccording to claim 9, characterized in that the controller is configuredto determine an amount of force applied to the sensing capacitor or anacceleration of the sensing capacitor applied to the sensing capacitorbased on the change of charge of the at least one sensing capacitor. 11.Apparatus according to claim 7, characterized in that the PCB comprisesat least two longitudinal cuts arranged in parallel to each other, andwherein the at least one sensing capacitor is coupled to the PCB betweenand equally spaced from the at least two longitudinal cuts. 12.Apparatus according to claim 7, characterized in that a first sensingcapacitor is coupled to a first side of the PCB and a second sensingcapacitor is coupled to a second side opposite to the first side of thePCB, wherein the first and the second sensing capacitor are coupled tothe PCB adjacent or directly opposite to each other.
 13. Apparatusaccording to claim 12, characterized in that the PCB is of alongitudinal shape having a first end and a second end opposite to thefirst end and two longitudinal ends, wherein the first end is affixableand the second end is moveable, and wherein a charge amplifier or partsof a charge amplifier are connected between at least one of the firstand second sensing capacitors and the controller, and wherein thecontroller is coupled to the PCB adjacent to the first end and whereinthe first and the second sensing capacitor is coupled in a firstdistance from the first end to the PCB.
 14. Apparatus according to claim11, characterized in that the controller is configured to determine anoscillation of the PCB based on an amount of force applied to the firstand the second sensing capacitor based on the change of charge of thefirst and the second sensing capacitor.
 15. Apparatus according to claim7, characterized in that the PCB is of a longitudinal shape having afirst end and a second end opposite to the first end and twolongitudinal ends, wherein the first end is affixable and the second endis rotatable, and wherein the two conductors and the dielectric of theat least one sensing capacitor is coupled to the PCB vertically to therotation axis of the PCB; the controller is configured to determine atorsion force applied to the sensing capacitor based on the change ofcharge of the at least one sensing capacitor; the PCB is of alongitudinal shape having a first end and a second end opposite to thefirst end and two longitudinal ends, wherein the first end is affixableand the second end is moveable, and wherein the at least one sensingcapacitor is coupled to the PCB adjacent to and spaced from the firstend of the PCB in a first distance, and wherein the charge amplifier iscoupled to the PCB adjacent to and spaced from the first end of the PCBin a second distance, the second distance being smaller than the firstdistance; and wherein the controller is configured to determine avibration of the sensing capacitor based on the change of charge of theat least one sensing capacitor.
 16. Apparatus according to claim 7,characterized in that the PCB is arranged within a pressure cell, andwherein the PCB divides the pressure cell into a first and a secondpressure chamber, and wherein the first pressure chamber comprises afirst opening for applying a first pressure to the first pressurechamber and the second pressure chamber comprises a second opening forapplying a second pressure to the second pressure chamber, and wherein afirst sensing capacitor is coupled to a first side of the PCB and asecond sensing capacitor is coupled to a second side opposite to thefirst side of the PCB, wherein the first and the second sensingcapacitor are coupled to the PCB adjacent or directly opposite to eachother. the controller is configured to determine a differential pressureapplied to the first and the second sensing capacitor based on thechange of charge of the first and the second sensing capacitor; the PCBis of a longitudinal shape having a first end and a second end oppositeto the first end and two longitudinal ends, wherein the first end isaffixable and the second end is moveable, and wherein the two conductorsand the dielectric of the at least one sensing capacitor is coupled tothe PCB in parallel to the two longitudinal ends; and the controller isconfigured to determine a pulling force applied to the second end of thePCB based on the change of charge of the at least one sensing capacitor.17. Apparatus according to claim 1, characterized in that the at leastone sensing capacitor is a ceramic capacitor or a silicon capacitor. 18.Apparatus according to claim 7, characterized in that the at least onesensing capacitor is coupled to the PCB by using integrated circuittechnology.
 19. Apparatus comprising: at least one sensing capacitor,and a controller, wherein the controller is configured to receive asignal from the at least one sensing capacitor indicative of a change ofcharge of the sensing capacitor, and wherein the controller isconfigured to determine an amount of force applied to the sensingcapacitor, an acceleration of the sensing capacitor, a torsion of thesensing capacitor, a vibration of the sensing capacitor or a pullingforce applied to the sensing capacitor based on the change of charge ofthe at least one sensing capacitor, and wherein a charge amplifier isconnected between the at least one sensing capacitor and the controllerand wherein the charge amplifier comprises at least a first operationalamplifier, and wherein the at least one sensing capacitor is coupled toa printed circuit board (PCB).
 20. A method comprising: measuring achange of charge of a of a sensing capacitor; and determining an amountof force applied to the sensing capacitor, an acceleration of thesensing capacitor, a torsion of the sensing capacitor, a vibration ofthe sensing capacitor or a pulling force applied to the sensingcapacitor based on the change of charge of the at least one sensingcapacitor.